Three-body forces and proton-rich nuclei

We present the first study of three-nucleon (3N) forces for proton-rich nuclei along the N=8 and N=20 isotones. Our results for the ground-state energies and proton separation energies are in very good agreement with experiment where available, and with the empirical isobaric multiplet mass equation. We predict the spectra for all N=8 and N=20 isotones to the proton dripline, which agree well with experiment for 18Ne, 19Na, 20Mg and 42Ti. In all other cases, we provide first predictions based on nuclear forces. Our results are also very promising for studying isospin symmetry breaking in medium-mass nuclei based on chiral effective field theory.Comment: 5 pages, 4 figures, minor changes, published versio

Abundance and distribution of larval fishes and shrimps in the Laguna Madre, Texas : a hypersaline lagoon

To Texas Water Development BoardContract nos. IAC (88-89)1636 and (90-91)0751October 1990Tidal inlets connecting the Gulf of Mexico with estuarine waters are widely spaced and relatively narrow along the Texas coast. These inlets provide the sole route for ingress of larvae to the estuary for estuarine-dependent marine species and the egress of juveniles and sub-adults of these species back to the ocean. This study was an investigation of the abundance and distribution of ichthyoplankton of selected fishes and shrimps in an area where the opening and maintenance of a new tidal pass has been proposed in the Laguna Madre, a sub-tropical, hypersaline lagoon along the southern Texas coast. Surface and bottom ichthyoplankton samples were taken bimonthly in four zones in the Laguna Madre in areas which were directly influenced by tidal inlets from the Gulf of Mexico and areas isolated from such connections. Seasonal composition of the ichthyoplankton was similar to that reported from other Gulf of Mexico and southeastern United States estuaries with winter catches dominated by offshore spawners and summer catches dominated by inshore and estuarine spawners. The pelagic larvae of three species of estuarine spawners, bay anchovy (Anchoa mitchilli), spotted seatrout (Cynoscion nebulosus), and black drum (Pogonias cromis), were common throughout the Laguna Madre at salinities up to 50°/00. Pelagic larvae of offshore spawners were abundant only in the area near the tidal inlet and only a few individuals were found dispersed throughout the lagoon. The majority of these species are distributed throughout the Laguna Madre as juveniles but the dispersion or advection of these species to areas not closely associated with tidal inlets occurs at development stages older than the pelagic larval stage. These data suggest that opening and maintaining a tidal inlet in the upper Laguna Madre would increase the opportunity for recruitment of larvae of offshore spawners into an area currently unoccupied by these life-history stages.Marine Scienc

Three-nucleon forces and spectroscopy of neutron-rich calcium isotopes

We study excited-state properties of neutron-rich calcium isotopes based on chiral two- and three-nucleon interactions. We first discuss the details of our many-body framework, investigate convergence properties, and for two-nucleon interactions benchmark against coupled-cluster calculations. We then focus on the spectroscopy of 47-56Ca, finding that with both 3N forces and an extended pfg9/2 valence space, we obtain a good level of agreement with experiment. We also study electromagnetic transitions and find that experimental data are well described by our calculations. In addition, we provide predictions for unexplored properties of neutron-rich calcium isotopes.Comment: 15 pages, 22 figures, published versio

Nuclear forces and their impact on neutron-rich nuclei and neutron-rich matter

We review the impact of nuclear forces on matter at neutron-rich extremes. Recent results have shown that neutron-rich nuclei become increasingly sensitive to three-nucleon forces, which are at the forefront of theoretical developments based on effective field theories of quantum chromodynamics. This includes the formation of shell structure, the spectroscopy of exotic nuclei, and the location of the neutron dripline. Nuclear forces also constrain the properties of neutron-rich matter, including the neutron skin, the symmetry energy, and the structure of neutron stars. We first review our understanding of three-nucleon forces and show how chiral effective field theory makes unique predictions for many-body forces. Then, we survey results with three-nucleon forces in neutron-rich oxygen and calcium isotopes and neutron-rich matter, which have been explored with a range of many-body methods. Three-nucleon forces therefore provide an exciting link between theoretical, experimental and observational nuclear physics frontiers.Comment: 28 pages, 13 figures, 1 tabl

New Prospects in Fixed Target Searches for Dark Forces with the SeaQuest Experiment at Fermilab

An intense, 120 GeV proton beam incident on an extremely long, iron target generates enormous numbers of light-mass particles that also decay within that target. If one of these particles decays to a final state with a hidden gauge boson, or if such a particle is produced as a result of the initial collision, then that weakly interacting, hidden-sector particle may traverse the remainder of the target and be detected downstream through its possible decay to an $e^+e^-$, $\mu^+\mu^-$, or $\pi^+\pi^-$ final state. These conditions can be realized through an extension of the SeaQuest experiment at Fermilab, and in this initial investigation we consider how it can serve as an ultrasensitive probe of hidden vector gauge forces, both Abelian and non-Abelian. A light, weakly coupled hidden sector may well explain the dark matter established through astrophysical observations, and the proposed search can provide tangible evidence for its existence --- or, alternatively, constrain a "sea" of possibilities.Comment: 14 pages, 8 figures; improved sensitivity analysis and cross-checks; small shifts in the expected limits; conclusions unchanged; refs. adde

Exploring sd-shell nuclei from two- and three-nucleon interactions with realistic saturation properties

We study ground- and excited-state properties of all sd-shell nuclei with neutron and proton numbers 8 <= N,Z <= 20, based on a set of low-resolution two- and three-nucleon interactions that predict realistic saturation properties of nuclear matter. We focus on estimating the theoretical uncertainties due to variation of the resolution scale, the low-energy couplings, as well as from the many-body method. The experimental two-neutron and two-proton separation energies are reasonably well reproduced, with an uncertainty range of about 5 MeV. The first excited 2+ energies also show overall agreement, with a more narrow uncertainty range of about 500 keV. In most cases, this range is dominated by the uncertainties in the Hamiltonian.Comment: 6 pages, 4 figure

Comparison of rocket-borne probes for electron density measurements Quarterly status report no. 5, Aug. 1 - Oct. 31, 1965

Impedance, resonance, capacitance, electrostatic, and Langmuir probe performance for ionospheric electron density profil

Past and Ongoing Tsetse and Animal Trypanosomiasis Control Operations in Five African Countries: A Systematic Review

Background Control operations targeting Animal African Trypanosomiasis and its primary vector, the tsetse, were covering approximately 128,000 km2 of Africa in 2001, which is a mere 1.3% of the tsetse infested area. Although extensive trypanosomiasis and tsetse (T&T) control operations have been running since the beginning of the 20th century, Animal African Trypanosomiasis is still a major constraint of livestock production in sub-Saharan Africa. Methodology/Principal Findings We performed a systematic review of the existing literature describing T&T control programmes conducted in a selection of five African countries, namely Burkina Faso, Cameroon, Ethiopia, Uganda and Zambia, between 1980 and 2015. Sixty-eight documents were eventually selected from those identified by the database search. This was supplemented with information gathered through semi-structured interviews conducted with twelve key informants recruited in the study countries and selected based on their experience and knowledge of T&T control. The combined information from these two sources was used to describe the inputs, processes and outcomes from 23 major T&T control programmes implemented in the study countries. Although there were some data gaps, involvement of the target communities and sustainability of the control activities were identified as the two main issues faced by these programmes. Further, there was a lack of evaluation of these control programmes, as well as a lack of a standardised methodology to conduct such evaluations. Conclusions/Significance Past experiences demonstrated that coordinated and sustained control activities require careful planning, and evidence of successes, failures and setbacks from past control programmes represent a mine of information. As there is a lack of evaluation of these programmes, these data have not been fully exploited for the design, analyses and justification of future control programmes